Stiffener material for shoes



Sept. 3, 1963 s. M. GRlswoLD STIFFENER MATERIAL FOR SHOES Filed March 15, 1961 Inventor United States Patent O 3,102,837 STHFFENER MATERIAL FR SHES Stanley M. Griswold, Newton, Mass., assigner, by mesne assignments, to United Shoe Machinery Corporation, Boston, Mass., a corporation of New Jersey Filed Mar. 13, 1961, Ser. No. 95,423 8 Claims. {Ch 162-108) This invention relates to improvements in solventactivatable sheet stiiirener material, particularly material for stiffening end portions of shoes and in a method of making such material.

In my co-pending application for United States Letters Patent, Serial No. 847,550, tiled October 20, 1959, there is disclosed a solvent-activatable sheet stiifener material comprising a water-laid layer of intermixed fibers and particles of `a stiiiening agent soluble at room temperature in lan organic solvent. The layer is formed by draining a furnish of fibers containing stifiening agent particles dispersed therein through a thin, relatively open brous sheet to which the layer becomes attached by interspersion of iibers. This composite sheet material is effective for its intended purposes and is low in cost.

However, there has been some tendency for displacement of stifiener particles from surface portions of the stiffener material; and although the loss of stiffener particles is not great enough to interfere with the operation of the material, nevertheless, it is undesirable. A further diiiiculty has been a tendency of the sheet to delamination during handling prior to activation.

In my prior copending application for United States atent, Serial No. 817,191, iiled June l, 1959, now US. Patent 3,021,240 of February 13, 1962, there is disclosed a treatment of such a stiifener sheet which in some measure eliminates these difliculties. The treatment there disclosed involves application of -a limited amount of solvent to the stiffener sheet in semi-isolated areas on a surface of the sheet material yas by spattering or by use of a knurled roll. This treatment produces inthe material, beneath the areas of activation, a partial fusion of the stiffening agent particles in an inclusive formation narrowing in cross section depthwise of the material. The

`effect of this treatment is to render the material liirner and to reduce dusting, -i.e. loss of stiliener particles to a considerable extent. However, areas which have not been solvent treated are still prone to lose stiiiener particles and the speed of activation of the sheet by solvent andthe development of a tacky surfae is interfered with to some extent since the prior solvent ltreatment of the stiffener particles has altered their shape and caused limited agglomeration so that they are no longer as available to attack by solvent as in their original condition. Also, since the incursive formations narrow in cross section depthwise of the material, the firming of the material is irregular and the ability to be skived may not be satisfactory for all purposes.

It is an object of the present invention to provide economical water-laid sheet material comprising fibers and coalescible particles of plastic which is more resistant to loss of particles of stiffening agent without loss of ability to develop surface tack on activation and which possesses improved ability to be skived to a uniform thinly tapering edge.

To this end and in accordance with a feature of the invention, the character of the sheet stiffener is improved and displacement of stiflener particles is substantially eliminated by holding the bers and particles in iassociated relation by binder deposited on said fibers and particles but not closing or markedly interfering with the existing porous nature of the sheet stiffener material.

The application of binders to fibrous sheet material presents special problems where it is necessary that the sheet remain porous for later impregnation by a solvent activator. Treatment of surfaces of stiiiener sheet material with organic solvent solutions involves the difficulties of using a solvent which will not attack the stiffener particles, and of avoiding the development of an irnpervious surface coating of binder while at the same time securing the desired deposit in depth of the binder on the fibers and particles. Treatment of stiffener sheet material with yan aqueous dispension of a binder ordinarily results in a deposit of the binder material only in a thi-n layer near the surface. Here also the desired depth of impregnation has not been obtained.

It is a further object of the present invention to provide a simple and inexpensive method for making a waterlaid sheet of fibers and stiffener particles in which the binder will penetrate and effect the desired action on fibers and particles and give the desired character of sheet throughout at least a substantial portion of the thickness of the sheet stiffener material.

To this end and in Iaccordance with a further feature of the invention, an aqueous dispersion of iibers and coalescible particles of a water insoluble plastic is strained through a forarninous surface to form a layer of fibers with particies distributed therethrough, and the web so obtained is treated, while still wet, with an aqueous dispersion of a binder to impregnate the web to `a depth of a substantial portion of its thickness. On drying the impregnated web, the binder forms a coherent deposit on the fibers and particles to hold them in associated relation Without significantly reducing the porosity of the web. This deposit in depth provides a marked irnprovement in the ability of the stiffener sheet material to be skived. Also, the binder material in the impregnated portion is in a form and location readily acted on by solvent to create a tacky surface on the stiifener material when the material is activated by solvent.

Other features yand advantages of the invention will be understood more fully from the following detailed description taken in connection with -accompanying drawings in which:

FIG. 1 is a partial section, greatly enlarged, of a sheet of stitiener material constituting one embodiment of the present invention;

FIG. 2 is an exploded angular View of a portion of a sheet of the type shown in FIG. l;

FIG. 3 is a diagrammatic elevational View, with parts broken away, of a modied screen cylinder type papermaking machine illustrating the manufacture of a sheet material according to the present invention; and

FIG. 4 is `a partial section, greatly enlanged, of Ia laminate of two composite sheets of intermiXed fibers and plastic particles constituting another embodiment of the present invention.

Referring to FIGS. l `and 2, the sheet material of the present invention comprises a layer 10 of fibers in which is incorporated coalescible particles of a plastic such as an organic solvent soluble stiifening agent, the layer being formed by ltration from a suitable furnish through =a sheet 12 of relatively open, fibrous fabric so that bers of the layer 10 and the sheet 12 are interspersed at the interface 1.4 (FIG. 2). Binder material is deposited on the fibers land particles in ya portion 16 of the layer 10 from the surface of the layer 10 opposite the: sheet 12 depbhwise into the layer a substantial portion of the entire thickness `of :the layer, preferably -at least one-third of the thickness.

The fiber content of the layer 1G may comprise any suitable papermaking fibers or mixture of fibers such yas cotton, nylon, jute, hemp, hair, vvool, kraft or sulfite pulp or asbestos. I yhave found that kraft paper pulp fibers amasar have adequate strength and form a very satisfactory product. v

The plastic material used in a sheet material intended for shoe stiifening suitably comprises particles of a normally solid, resilient, high molecular weight materia-l soluble at roo-rn temperature in a volatile organic so-lvent and may include, for example, organic solvent soluble resinous polymers and copolymers of ethylenically unsaturated monomers such as, the monovinyl aromatic hydrocarbons of the benzene series including polystyrene and polyvinyl toluene, polyvinyl acetate and the acrylate and methacrylate polymers. Cellulose derivatives, such as cellulose acetate, natur-al resins, ysuch as modified rosin and the like may .also be used alone or in combination. For uses other than shoe stilfening, the foregoing or other coalescible plastics insoluble in the furnish may be used alone or -in mixtures depending on the properties desired.

The furnish 1S is an aqueous dispersion and ordinarily the plastic particles will be selected from largely or entirely Water-insoluble materials. However, it is also possible to introduce additives to the furnis-h which reduce the solubility "of desirable plastics possessing some solubility in water.

The particles of plastic maybe produced by pulverizing scrap plastic material, -for exainple the scrap resulting from 'the manufacture of polystyrene lenses which is now commonly available. polystyrene and polyvinyl toluene may also be employed in the form of small beads made by known suspension polymerization techniques.

It has been found .that the presence of the plastic parfticles materially increases the ease of draining of the furnish over identical furnishes not containing the plastic particles. Also, the size and shape of the plastic particles has an effect |both on the ease of the draining of the furnish, on the ability of the dried materia-l to accept solvent yand on the softening effect of the solvent.

Thus, polystyrene particles produced by pulverizing scrap polystyrene lens material in a rotary pulverizer have typically a particle size distribution extending yfrom the size of the pulverizer screen openings down to fine powder. Such pulverized material, mixed with water and fiber in a furnish and strained on a screen, usually produces -a sheet somewhat more dense, with slower filtration land slower uptake of activating solvent than a sheet made with plastic in the form of fairly uniform beads of equivalent size. These differences are accentuated where the larger particles `are screened out of the pulverized material. On the other hand, small pulverized particles or beads in a sheet tend to soften more rapidly upon application of solvent than larger particles or Ibeads because rof the `greater surface to volume ratio. It has been found that in order to obtain effective draining of liquid from the fiber and particle layer deposited on a screen `to enable rapid yand economical manufacturing yand at the same time to form a sheet which is readily and completely activat- -able by solvent within the time available in shoe manufacturing processes, it is important that the particle size distribution be las follows: at least 98% passing a No. 40 sieve, 70% to 90% passing a No. 100 sieve, and from to 30% passing a No. 170 sieve, the percentages being by weight of the original mass of particles and the sieves being of the Standard Screen Series, U.S. Bureau of Standards, 1919.

The proportion of plastic particles to fiber may tbe varied considerably, but for most purposes l find that a ratio of about 1 to 5 parts by weight of plastic particles to one part of fiber is most suitable.

In making a sheet according to one form of the present invention, the plastic particles `and fiber are beaten up with a suitable quantity of water to form an aqueous dispersion or furnish. The lfurnish is strained through a sheet 12 of relatively open fibrous fabric disposed on a support, usually a wire -screen 20. However, the function of the screen being merely to `support the fibrous Many plastic materials including i fabric sheet i2, it may conveniently have a larger mesh than usual paper making screens. In fact, the support for the facing sheet may -be in any form which provides suitable backing for the sheet 12 while permitting filtration kthrough the brous fabric sheet.

The fibrous fabric sheet 12 should be thin, relatively open Iand `flexible yet strong. The open character of the sheet is important in relation to its filtering yfunction in permitting drainage of the water of the furnish while holding back the fiber and plastic particles. This character is also involved in providing adequate attachment of the sheet i2 and the layer 10` of fibers deposited thereon since an open sheet permits, during such filtration, interspersion of fibers of the sheet and of the water-laid fibrous layer so that when dry the interspersion of the fibers forms a means of attachment ybet-Ween the -sheet and the layer deposited thereon. The sheet 12 may bewoven or nonwoven and may be made from cotton, hemp (eg. rope paper) or other fibers. `lf any bonding agent is used in a nonwoven fabric, it should be insoluble in water so that the fibers ywill not disintegrate. An inexpensive Woven fabric such as tobacco cloth may be employed. Relatively open non-woven rayon fiber fabric is also useful. This fabric `comes in a number of weights and thicknesses ranging from about 8 to 30' grams per square yard and from about 3 to about `tl mils in thickness. I have found suitable fabric which is about 8 grams per square yard in weight and about 31/2 mils in thickness.

After sheeting out the `furnish to form a layer of desired thickness, water may be removed mechanically from the sheet to reduce the amount which must later be evaporated. Removal of water may be effected by suction and/ or lby squeezing the sheet between rolls 22. While the composite sheet is still wet, an aqueous dispersion of a binder is applied preferably by a reverse rotating coating roll 24 to the surface of the sheet opposite the surface on which the fabric 12 is secu-red. It appears that the water content of the web holds the fibers in a Vmore extended relation than would be the case in a dry web and also the water eliminates difliculties caused by dry webs, particularly difficulties of penetration of the binder dispersion into the fiber layer.

The binder may be any liquid solution or dispersion of a material capable of `forming a coherent deposit to hold the fibers and particles together. But it is preferred to use a binder which will have certain rubbery 'characteristics for more effective improvement of the hand of the sheet, i.e. will have the ability to hold the iibers and particles together even where the sheet is subjected to limited liiexing. Likewise, it is desirable that the `binder be capable of at least partial solution or swelling to a tacky condition when the stiffener is activated by organic solvent. A rubbery copolymer of styrene and butadiene containing from about 30% to 50% of butadiene is a desirable component of the binder and is readily commercially available as a latex, i.e. an aqueous dispersion. It is found that -the ability to develop surface tack, the eiectiveness of Vthe binder as an aid in improving the character of the stiifener sheet before activation, and in increasing strength and stiffness after activation are improved through the incorporation with the rubbery copolymer latex of a substantial proportion of a latex of a high styrene content butadiene-styrene copolymer, i.e., a copolymer in which the styrene content may be from 50 to 95%. Suitable mixtures of the latices may comprise from about 30% to about 90% by weight solids of the rubbery copolymer with about 10% to 70% by iweight solids of the high styrene content copolymer. Latices having a solids content of from about 5% to 15% have been found useful for impregnating a yfiber and plastic particle layer according to lthe present invention. Effective impregnation `to achieve the desired results has involved applying from about 0.2. to about 2 oz. of the copolymer solids per sq. ft. of the layer. This impregnation will penetrate at least 1A of the thickness of the layer and may extend throughout the thickness of the layer.

After impregnation, the sheet is then dried and may then be 'rolled to smooth and compact it to about 2/s of its original thickness.

Laminated sheet material constituting another aspect of the present invention (see FIG. 4) includes two or more composite sheets comprising a water-laid layer of intermixed fibers and plastic or resinous particles and an open woven or non-woven reinforcing fabric 12, the fibers of the fibrous layer 10 being interspersed with fibers of the fabric 112 to form a mechanical union holding the layer 10 and the fabric 12 together. A second composite sheet of a water-laid layer i101 of intermixed fiber and plastic or resinous particles and fabric 12 is secured to the first composite sheet by a layer 26 of `an adhesive with the fabric layers adjacent. An adhesive will be used which is not unduly softened by solvent to `which the laminate may be exposed. Preferably the adhesive is somewhat rubbery to insure that the laminate is flexible and is resistant to delamination when flexed.

Apparatus useful Ifor supporting the fabric sheet 12 for straining ia furnish 18 to form a felted fibrous sheet 10, comprises ia modified cylinder-type .pa-permaking machine 28 diagrammatically illustrated in FIG. 3. As there shown, the machine 28 comprises a vat 30 with a flow box 32 at one end for insuring Va smooth supply of `furnish to the interior of the vat 30. The flow box 32 is of conventional type comprising a bottom wall 34 and an end wall 36 of which the upper edge 38 is adjustable heightwise to regulate flow Iof furnish from the interior of the flow ybox 32 to the interior of the vat 30'. The bottom wall 3d and end wall 36 extend across the interior of the vat 30 and cooperate with the side walls 40 and end wall 42 of the vat 30 to define a chamber ddinto which furnish is fed through the pipe d6. A cylinder 43 is rotatably mounted in the vat 30 and is provided with means for driving it (not shown). A pipe 50 yfor withdrawing liquid is disposed in `the interior of the cylinder 48. The cylinder 4d differs lfrom conventional papermaking cylinders in that the .wire screen on its surface is of substantially larger mesh. It is `desirable that the openings in the screen be at least about 1/6 greater than the dimension |of the largest plastic or resin particles of the furnish to prevent plugging of the screen lby the particles. 1t should be noted that the screen openings may in some instances be somewhat reduced by reinforcing wires and the screen opening size referred to is the `actual screen opening. Depending on the size of the plastic particles, there may be used screens from size No. 12 to size No. 30 (U.S. Bureau of Standards, Standard Screen Series, 1919).

For the first operation to form a mechanically linked fabric and felted fiber-plastic particle sheet, fabric 12 is withdrawn from a roll 52, passed around a roller Sd which lays it down on the screen 20 or the cylinder 48 and the fabric 12 is carried around the cylinder 48 by rotation of the cylinder. As shown in PlG. 3, the water component of the furnish passes through the fabric 12 to the interior of the cylinder 4S leaving behind a layer 10 of intenmixed fibers and plastic particles. Fibers from the furnish 18 deposited on the fabric 12 penetrate and become entangled with the fibers of the yfabric 12 to attach mechanically the deposited intermixture :of fibers and plastic particles to the fabric `12. When the fabric 12 and the attached felted layer 10 of fibers and plastic particles have passed nearly around the cylinder 48, they are lifted from the surface of the cylinder by a couch roll 56 and felt 5S and carried up with the felt over the rollers 60 and 62. From the roller 62, the composite of the fabric 12 and felted layer `1i) is passed between squeeze .rolls-22 which mechanically express a portion of the water content and tfhen passes over a coating roll 24 tof which the lower portion dips into a Ibody 64 of binder liquid in the tray 66. The roll 24 rotates in a direction so that its surface is moving counter to the direction of movement of the composite sheet so that substantially the entire quantity of binder liquid picked up by the surface of the roll 24 is transferred and serves to impregnate the fiber layer 10.

After the step of impregnation, the sheet is dried by suitable drying means such as heated drying rollers 68.

Where a laminated stiiener is to be manufactured, the surface of the fabric 12 of a composite sheet is coated with a fhigh'viscosity adhesive layer 26. Useful adhesives include natural o-r synthetic rubber latices. After lapplication of the layer 26 of this adhesive, to the fabric 12, the fabric covered surface of a second composite sheet is pressed against the adhesive layer 26 and the adhesive allowed t-o dry to form a firm -bond between the two sheets.

The fol-lowing example is :given to aid in understanding the invention, but it is to Ibe understood that the invention is no-t restricted to the particular materials, purposes or procedures set forth in the example.

Example-A furnish was prepared by beating kraft pulp in water using a Hollander type beater device. The furnish was ladjusted to a fiber content of 0.14% fiber and there was then introduced polystyrene beads of which 100% pass through a No. 16 screen (screen opening 0.047), 99.7% pass through a No. 40 screen (screen opening 0.0i165), 90% pass through ra No. 100 screen (screen opening 0006"), 'and 15 pass through a No. 170 screen (screen opening .0035) in amount to bring the resin content of the lfurnish to 0.35%.

Tobacco cloth was drawn from a roll and laid down on the screen of a cylinder type papermaking machine .by a roll resting on the screen at the top of .the cylinder. The screen was No. 14 (screen `opening 0.0555). The cloth was brought around the cylinder and around a couch roll and felt `at the top of the cylinder.

The cylinder which was 18 in diameter was set in rotation at about 3 rpm. and furnish introduced into the ow box of the machine to fill the vat of the machine nearly to within 2" of the top of the cylinder. '111e white water yfrom the furnish strained through the cloth on the cylinder screen leaving behind a layer of intermixed fiber and resin. The liquid entering the inte-rior of the cylinder was withdrawn. The layer of intermixed fiber and resin particles increased in thickness as it passed around the cylinder and was lifted off the screen as Ia composite sheet by the couch roll and felt. The composite sheet was passed between rolls to squeeze water from it. In the i sheet, the Vfibers of the intermixed fiber and resin particle layer were interpersed with the fibers of the tobacco cloth to an extent sufficient to Ihold the ber and resin particle layer firmly to the tobacco cloth.

7.8 gallons of a 40% solids latex of a copolymer of equal parts by weight of butadiene and styrene and 7.8 gallons of `a `45% solids latex of a copolymer 80% styrene and 20% butadiene were mixed with 3.9 gallons of a 10% solution of Aquarex-D and 80.5 gallons of water. The mixture was supplied to the tray into which the coating roll dipped. The composite sheet of intermixed fiber and resin particle layer and tobacco cloth was passed over the coating roll with the fiber and resin particle layer against the roll. The roll rotated in a direction so that its surface moved -counter to the direction of movement of the composite sheet andthe surface of the roll picked up the mixed latex composition from the tray and deposited it on the surface of the layer. It was observed that the deposited latex penetrated into the surface of the layer promptly after application. The speed of the roller was controlled to provide a deposit of about .6 oz. of solids of the latex per square foot of the composite sheet.

After the step of impregnation, the sheet was dried by passing it around the heated drying rollers.

The dry composite sheet was coated on the cloth side with a thickened natural rubber latex (60% solids) an excess of the latex being applied and scraped off with a doctor blade. Thereafter a second composite sheet was assembled with its fabric surface against the deposit of rubber latex on the first composite sheet.

After the latex adhesive had set, a boX toe blank was cut from the laminate. The edges of the box toe blank were skived in a standard skiving machine and it was found that a thin uniform firm edge was obtained. The surfaces of the blank did not tend to lose the particles of the resin :and the sheet itself was capable of the flexing normally encountered in shoe making procedures without del-amination. The box toe blank was treated with a solution comprising 8 parts of methyl ethyl ketone and 16 parts of toluol. The solution rapidly and completely penetrated `and softened the laminate and brought the Surfaces of the laminate to a tacky condition. The activated blank was placed in the toe of the shoe, the shoe Was lasted and the stifiener allowed to harden. rThe toe of the shoe was found to be stific and resilient and to maint-ain its shape under the conditions encountered in use.

Having thus described my invention, what I claim as new land desire to secure by Letters Patent of the United States is:

1. In a hardenable sheet material for stiffening end portions of shoes comprising a porous layer of Water-laid bers intermixed with discrete particles of norm-ally solid, organic solvent-soluble coalescible stiiiening agent with said particles being present in the ratio of from about 1 to about 5 parts by Weight to l part by weight of fibers, the improvement including a coherent deposit of a binder on said fibers and particles from one surface in to a depth of a substantial portion of the thickness of said layer and holding said fibers and particles in associated relation but not closing the pores of said layer, said binder being swellable to tackycondition by an organic solvent activator for said sheet material.

2. In a hardenable sheet material for stifiening end portions of shoes comprising a porous layer of water-laid fibers intermixed with discrete particles of normally solid, organic solvent-soluble coalescible stiffening agent with said particles being present in the ratio of from about 1 to about 5 parts by weight to 1 part by weight of fibers, the improvement including a coherent deposit of a binder on said fibers and particles from one surface in to a depth of a substantial portion of the thickness of said layer and holding said fibers and particles in associated relation but not closing the pores of said layer, said binder comprising a rubbery copolymer of styrene and butadiene reduceable to tacky condition by an organic solvent activator for said sheet material.

3. In `a hardenable sheet material for stiffening end portions of shoes comprising a porous layer of waterlaid cellulosic paper-making fibers intermixed with coalescible discrete particles o-f normally solid, organic solvent-soluble thermoplastic polymer resin with said particles being present in the ratio of from about 1 to about 5 parts by weight :to 1 part by weight of fibers and a relatively open fibrous fabric on a face of said layer with fibers of said layer and bers of said fabric interspersed at the interface between them to provide a mechanical link holding said layer to said fabric, the improvement including a coherent deposit of a binder on said fibers and particles from the other face of said layer in to a depth of 1/3 of the thickness of said layer and holding ksaid fibers land particles in associated relation but not closing the pores of said layer, said binder comprising a rubbery copolymer of styrene and butadiene reduceable to tacky condition by an organic solvent activator for said sheet material.

4. In a hardenable sheet material for stiffening end portions of shoes comprising a porous layer .of waterlaid cellulosic paper-making fibers intermixed with coalescible discrete particles of normally solid, organic soltively open fibrous fabric on a face of said layer With fibers of saidlayer and fibers of said fabric interspersed at the interface between them to provide a mechanical link holding said layer to said fabric, the improvement including a coherent :deposit of a binder on said fibers and particles from the `other face of said layer in to a depth of 1/3 of the thickness of said layer and tholdin-g said fibers and particles in associated relation but not closing the pores of said layer, said binder comprising from about 30% to about 90% by Weight of a rubbery copolymer of styrene and butadiene and from about 10% to about 70% by Weight of a copolymer of butadiene and styrene in which the styrene content is from 50% to 75% reduceable to tacky condition by an organic solvent activator for said sheet material, said binder being present to the extent of from about 0.2 to about 2 ounces per square foot of the surface of said layer.

5. In a hardenable sheet rnaterial for stiening end portions `of shoes comprising a porous layer of waterlaid cellulosic papernnaking fibers intermixed wit-l1 coalescible discrete particles of lnormally solid polystyrene resin with said particles being present in the ratio of from about 1 to about 5 parts by weight to 1 part by weight of fibers and a relatively open fibrous fabric on a face of said layer `with fibers of said layer and fibers of said fabric interspersed at the interface between them to provide a mechanical link `holding said layer t-o said fabric, the improvement including a coherent deposit of a binder on said fibers and particles from the Vot-her face of said layer in to a depth of 1/a of the thickness of said layer and holding said `fibers and particles in associated relation, but not closing the pores of said layer, said binder com prising from about 30% to about 90% by weight of a rubbery copolymer of styrene and butadiene and from about 10% to about 70% by weight of a copolymer of butadiene and styrene in `which the styrene content is from 50% to 75% reduceable to tacky condition by an organic solvent activator for said sheet material, said binder being present to the extent of from about 0.2 to about 2 ounces per square foot of the surface of said layer.

6,ln a hardenable sheet material for stiffening end portions of shoes comprising a laminate of two cornposites of porous layer and open fibrous fabric, said composites being vheld in laminated relationship with the fibrous fabric covered surfaces adjacent to each other by a rubber base adhesive, said porous layers comprising water-laid cellulosic papermaking fibers intermixed with coalescible discrete particles .of normally solid polystyrene resin with said particles being present in the rati-o of fro-m about 1 to about 5 parts by weight to 1 part by weight of fibers and a relatively open fibrous fabric on a face of said layer with fibers of said layer and fibers of said fabric interspersed at the interface between them to provide a `mechanical :link holding said layer to said fabric, the improvement including coherent deposits of a binder on said fibers and particles from the other faces of said layers in to a depth of 1/3 of the thickness of said layers and holding said fibers and particles in associated relation, but not closing the pores of said layers, said binder cornprising from about 30% to about 90% by weight of a rubbery copolymer of styrene and butadiene and from about to about 70%V by weight of a copolymer of butadiene and styrene in which the styrene content is from 50% to 75 reduceable to tacky condition by an organic solvent activator for said sheet material, said binder being present to the extent of from about 0.2 to about 2 ounces per square foot of the surface of said layers.

7. In a method `of making hardenable sheet material for stiffening end portions of shoes comprising the steps of forming an aqueous dispersion of fibers and discrete particles of a normally solid thermoplastic water insoluble organic solvent-soluble coalescible stiffening agent, said particles being present in the ratio of from about one to amasar 9 about live parts by weight to :one part by weight of bers, straining the dispersion through a thin relatively open iibrous fabric on a forarninous surface to deposit on said fabric a layer of libers with said particles Adistributed therethrough and with `fibers of said layer interspersed with -bers of said fabric to provide a mechanical link holding said Ilayer to said fabric, removing Water` from the layer, consolidating said layer, removingthe cornpcsitel of fabric, liber and particles from said forarninous surface as a wet web,` the improvement including apply ing an aqueous dispersion of a binder to the surface of said wet web opposite` said fabric to impregnate said web to a depth of at least about Vone-third of the thickness of said layer and drying said web to form a coherent deposit of said binder on said fibers and particles to hold them in associated relation but not closing the pores of said layer,

said binder being sWellable to tacky condition by an or vinyl aromatic Ihydrocarbon of the benzene series, said particles being present in `the ratioof from about one to 25 about live parts by Weight to one part by weight of bers,

and said particles being of a size .distribution as determined with U.S. Standard Sieves in which at least 98% will pass through a No. 40 sieve, from about 70% to about 90% v Will pass through a No. 100 sieve and from about 10% l@ to about 30% will pass thnough a No. 170 sieve, straining the dispersion through a thin relatively open brous fabric 0n a forarninous surface to deposit on the fabric a layer of bers with said particles `distributed therethrough and With bers of said layer interspersed with fibers of said fabric to provide a mechanical link holding said layer to said fabric, removing Water lfrom the layer, consolidating said layer, removing the composite of fabric, fiber and particles i material.

a `References Cited in the le of this patent UNITED STATES PATENTS Hanley Apr. 13, 1937 

1. IN A HARDENABLE SHEET MATERIAL FOR STIFFENING END PORTIONS OF SHOES COMPRISING A POROUS LAYER OF WATER-LAID FIBERS INTERMIXED WITH DISCRETE PARTICLES OF NORMALLY SOLIDS, ORGANIC SOLVENT-SOLUBLE COALESCIBLE STIFFENING AGENT WITH SAID PARTICLES BEING PRESENT IN THE RATIO OF FROM ABOUT 1 TO ABOUT 5 PARTS BY WEIGHT TO 1 PART BY WEIGHT OF FIBERS, THE IMPROVEMENT INCLUDING A COHERENT DEPOSIT OF A BINDER ON SAID FIBERS AND PARITCLES FROM ONE SURFACE IN TO A DEPTH OF A SUBSTANTIAL PORTION OF THE THICKNESS OF SAID LAYER AND HOLDING SAID FIBERS AND PARTICLES IN ASSOCIATED RELATION BUT NOT CLOSING THE PORES OF SAID LAYER, SAID BINDER BEING SWELLABLE TO TACKY CONDITION BY AN ORGANIC SOLVENT ACTIVATOR FOR SAID SHEET MATERIAL. 